Photo-induced bending of amorphous As2S3 bulk and fiber driven by optical torque

We have shown that typical amorphous chalcogenides, As2S3 bulk with a thickness of 50–100 μm and fiber with a diameter of 100 μm, can be bent by controlling the orientation of linearly polarized light. The bending of the bulk and fiber with thickness and diameter comparable to the optical penetration depth is efficiently generated by irradiation with a light of 2.33 eV, corresponding to the optical bandgap of amorphous As2S3. We have evinced that the bent phenomena of the amorphous As2S3 bulk and fiber are dominantly due to photo-induced anisotropy, fluidity, and optical torque effects. Then, the optical torque when bending occurred on the As2S3 fiber was quantitatively evaluated as 10−7 N‧m in the case of 20 W/cm2 irradiation. The bending of the As2S3 bulk glass and fiber due to the temperature rise by bandgap light irradiation is not dominant.